This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
ACK acknowledgement
ARQ automatic repeat request
BCH broadcast channel
BS base station
CR cognitive radio
DL (or D) downlink (from base station to UE)
DwPTS downlink pilot timeslot
GP guard period
HARQ hybrid automatic repeat request
LTE long term evolution
NACK non-acknowledgement
PDCCH physical downlink control channel
PDSCH physical downlink shared channel
PHICH physical hybrid ARQ indicator channel
PUCCH physical uplink control channel
PUSCH physical uplink shared channel
QP quiet period
RAN radio area network
S sensing
SCH synchronization channel
SPS semi-persistent scheduling
TDD time division duplexing
TD-LTE time division-LTE
TV television
TVWS television whitespace
UE user equipment
UL (or U) uplink (from UE to base station)
UpPTS uplink pilot timeslot
WLAN wireless local area network
Recent expansion in wireless traffic volume and corresponding bandwidth scarcity will require network operators to continue increasing their wireless capacity. One promising technique is to use license-exempt frequency spectrum, sometimes also termed unlicensed band(s) or shared band(s). Examples of such license exempt bands include the ISM (industrial, scientific and medical) band in which IEEE 802.11 type networks (hereafter, WLAN) currently operate, and also what is known as television whitespaces (TVWSs), which is a very large amount of spectrum. Using this frequency spectrum is not a simple task in that, since the spectrum is license exempt, the spectrum will be in simultaneous use by different users operating according to different RATs (radio access technologies) such as LTE and WLAN.
Cognitive radio (CR) has received considerable research impetus because of its ability to efficiently utilize the unused “spectrum holes” in unlicensed bands without causing severe interference to primary users, and also to help solve the bandwidth scarcity problem and achieve higher data rates. Additionally, CR could be implemented to solve some coexistence issues by sensing surrounding radio environment and determining the optimal communication scheme to avoid interference.
However, deploying a network capable of cognitive radio is a difficult task.